Loud speaker



July 28, 1931. P. w. GUMAER LOUD SPEAKER Filed Sept. 19, 192

ATTORNEYS Patented July 28, 1931 UNITED STATES PATENT OFFICE PERCY W. GUMAER, OF WEST ENGLEWOOD, NEW JERSEY, ASSIGNOR T HOPKINS COR- PORATION, 0F JERSEY CITY, NEW JERSEY, A CORPORATION OF DELAWARE LOUD SPEAKER I Application filed September 19, 1925. Serial No. 57,425.

This invention relates to an improvement in loud speakers for radio apparatus, and has for an object to provide such a device which is of substantially disk form.

Another object consists in providing such a device which, while in substantially the form of a disk, increases in thickness gradually from its axis toward its periphery.

the plane of the line VV of Fig.

Another object consists in providing such a device which includes a means near its periphery to prevent loss and distortion of sound during the vibration of the loud speaker. v

Another object consists in providing improved means for supporting such a device.

A further object consists in providing certain improvements in the form, construction, material and arrangement of the several parts whereby the above named and other objects may elfectively be obtained.

Practical embodiments of the invention are represented in the accompanying drawings in which Fig. 1 represents a front view of the preferred form,

Fig. 2 represents a section taken in the plane of the line II-II of Fig. 1 looking in the direction of the arrows,

Fig. 3 represents a rear view of the device, partly broken away,

Fig. 4 represents an enlarged detail face view showing part of the means for. securing the loud speaker in operative relationship with the receiver,

Fig. 5 represents a detail section taken in 4 looking in the direction of the arrows,

Fig. 6 represents a View, partly in section and partly in elevation, taken subtsantiallv on the" line VI-VI of Fig. 4, looking in the direction of the arrows, and

Fig. 7 represents a detail central section showing a modified form of disk.

Referring to the form shown in Figs. 1 to 6 inclusive, the loud speaker proper includes a disk which is denoted by 1. i

This disk is preferably composed of wood,

and is so constructed that it is very thin near ing and, simultaneously,

Any suitable form of gradually increasing thickness from the axis toward the periphery may be adopted, but I prefer'to have the disk flat on one side and concave on the other, so that the gradual increase in thickness is obtained by curving one face of the disk from its axis toward its periphery. This formation of the disk is clearly shown in Fig. 2 of the drawings.

I have found that the best results known to me are obtained by gradually increasing the thickness of the disk from the center to its periphery by the employment of an exponential curve based upon a mathematical formula which may be expressed as follows:

Where T=thickness of disk at center t=thickness of disk at any point distance 1- from center of disk e=the mathematical Then. t: 2 0.41 I p The foregoing is intended by way of illusconstant 2.718 =I= tration, to make clear a specific advantageous embodiment of the invention.

When in use as a loudspeaker, the disk, of"

course, vibrates. This vibration inevitably tends, at any given instant, to slightly compress the air against which the disk is movthe air. on the opposite side of the disk. The result of this is that a slight vacuum is created at one side of the disk and a certain amount ofsound leaks over the peripheral edge of the disk into the said partial vacuum, which leakage. is caused partly bythe compression on,one side of the disk, and partly by the rarification on the'opposite side,

since the said two conditions work together. This is particularly noticeable in instances of long wave length. Such leakage of sound tends tolessen the volume and distort the tone, and I have devised means to obviate to slightly rarify the same, which means consists of a baffle, or ring, that is formed at, or secured to, the periphery of the disk 1. This baffle is marked 2, and it may advantageously be composed of fibrous material, such as paper, or other suitable material, preferably, however, in thin sheet form.

The said bafile is arranged so as to project laterally away from the periphery of the disk and substantially parallel to the direction of vibratory movement of the disk. It has been found important to locate the baffie so that it lies at an angle to the plane of the disk, as distinguished from lying substantially in the plane of the disk, and l have determined that an arrangement in which the baflle is substantially parallel to the direction of vibratory movement of the disk produces the best results.

Such a baflle is quite efiective in preventing the leakage of sound from either side of the vibratory disk to the other since, as the vibratory movement is quite rapid, the pres ence of the bafiie serves to obstruct such leakage for a sufficient length of time to eliminate its injurious effect upon the sound producing qualities of the loud speaker.

A bafile of this kind is not limited in its application to a loud speaker of the parti cular form shown and described herein, but may advantageously be used with any form of loud speaker which vibrates in such manner asto tend to cause leakage over its periphery as above described. It is, however, peculiarly suitable for and well adapted to the particular form of loud speaker herein set forth.

In constructing the device of the present invention, the baflie' 2 may be secured'by adhesive or tacks, or in any other suitable man'- ner, to the circumference of the diskl and be allowed to project laterally therefrom in either or both directions. I have found it desirable, largely from the point of view of appearance, to arrange the bafile 2 so that it is flush with the front surface of the disk 1 and'projectsonly in a rear direction, as well shown in 2 of the drawings. A feature of lmportance is to make the joint between the baflle anddisk air tight;

The vibrating disk which constitutes the loud speaker, should, of course, be secured to a suitable sound receiver, such as electrical or mechanical.

In the present instance a receiving unit, which may be of any well known or approved form, is denoted, as a whole, by 3, and it has the usual wire connection 4.

To this receiver is fastened, in any suitable manner, a three-armed spider 5.

Each arm of the spider 5 carries onlits' extremity an attachment arrangement for connection with the disk 1 and, as each of these arrangements is the same, only one will be described in detail. The disk 1 is bored to provide a hole 6 fitted to receive a bolt 7 that is carried by the end of the spider arm and provided, at its protruding end, with a nut 8. Two elongated clamps which are triangular in cross section, are arranged so that one is on each side of the disk 1 adjacent the hole 6. These clamps are marked 9, 9-, and it will be seen that the flat base of one clamp rests upon the arm of the spider 5 while the corresponding part of the other clamp abuts the nut 8. The bolt 7 pierces both clamps 9, but the ridge or operative edge of the clamps, at each side of the bolt 7, is left intact and engages the adjacent face of the disk 1 at each side of the hole 6.

This constitutes a firm and yet delicate clamping device for the purpose intended and, while it serves to support the disk with adequate strength, it does not sensibly prejudice the vibration of the latter.

As already indicated, the disk is provided with three holes 6 and there is an attachment arrangement such as described located at the end of each arm of the spider 5 for cooperation with each of the said holes.

An actuating rod 10 has one end secured to the oscillating magnet 11, or corresponding part of the receiver, in a well understood manner, while its other end is fast to the disk 1 as indicated at 12. This connection is provided in order to cause the receiver to vibrate the disk, as will be well understood by all those familiar with this art.

It has been found quite desirable to suspend the loud speaker from a wall or the like, as distinguished from mounting it on a bracket on a table or analogous support and, to this end I have provided a pair of eyes 13, 13 in the periphery of the disk, to which eyes is fastened a suitable cord 14..

By preference, all the parts of the device are made of metal, excepting the disk 1 and The modified form shown in Fig. 7 is the same as the preferred form, except that the baffle 2 is omitted.

l have found that a loud speaker of the character herein described gives improved results with respect to both volume and quality.-

Such improvement is obtained, to a degree,

when the disk of graduated thickness is used material and arrangement of the several parts without departing from the spirit and scope of my invention, and hence I do not intend to be limited to the details herein shown and described except as they may be included in the claims.

rea ers What ll claim is:

1. A loud speaker comprising, a substantially flat disk, said disk being thicker at its periphery than at its axis, and abafie located near the periphery of the disk and projecting laterally therefrom at an angle to the plane of the disk.

2. A loud speaker comprising, a substantially flat disk, said disk being concave on one side, and a baflie located near the periphery of the disk and projecting laterally therefrom at an angle to the plane of the disk.

3. A loud speaker comprising, a substantially flat disk, said disk being thicker at its periphery than at its axis, and a bafie located near the periphery of the disk and projecting laterally therefrom in a direct-ion substantially parallel to the direction of vibratory movement of the disk.

4. A loud speaker comprising, a substantially flat disk, said disk being concave on one side, and a baffle located near the periphery of the disk and projecting laterally therefrom in a direction substantially parallel to the direction of vibratory movement of the disk.

5. A loud speaker comprising, a disk having one side substantially flat and the other side concave, and a peripheral baffle secured to the disk with one edge flush with the substantially flat side of the disk and the other edge protruding beyond the concave side of the disk.

6. A loud speaker comprising, a disk substantially flat on one side and concave on the other side, and a receiving unit mounted upon the concave side thereof.

7. A loud speaker comprising, a disk substantially flat on one side and concave on the other side, the thiclmess of the disk at any point other than the center being determined by theformula T6 in which T represents the thickness of the disk at its center, 6 represents the mathematical constant 2.718***F and 1' represents the radial distance of the rectly in the surrounding air clearly audible point from the center.

8. A loud speaker comprising a diaphragm having suflicient area to produce directly in the surrounding air clearly audible sounds or tones throughout the gamut of audible frequencies when actuated by impressed vibratory energy of audible frequency, and means for impressing vibratory energy on said diaphragm, said diaphragm having a plurality of zones which progressively increase in thickness from the zone atwhich the vibratory energy is impressed on the diaphragm whereby the zone where the energy is impressed is freely responsive to the higher frequencies and the other zone or zones are freely responsive to the lower frequencies.

9. A loud speaker comprising a diaphragm having suificient area to produce disounds or tones throughout the gamut of audible frequencies when actuated by imener is im ressed is freel res onsive to the higher frequencies and the other zone or zones are freely responsive to the lower frequencies.

10. A loud speaker comprising a diaphragm having suflicient area to produce directly in the surrounding air clearly audible sounds or tones throughout the gamut of andible frequencies when actuated by impressed vibratory energy of audible frequencies, said diaphragm having polar, intermediate and peripheral zones said zones progressively increasing in mass from the polar zones where by the polar zone is freely responsive "to the higher frequencies, the intermediate zones are freely responsive to the intermediate frequencies and the peripheral zones are freely responsive to the lower frequencies so as to produce in the regenerated sounds a balance of high and low tones substantially identical with the balance of those tones in the original sounds, and means for impressing vibratory energy on said diaphragm at the polar zone.

11. A loud speaker comprising a diaphragm having sufficient area to produce directly in the surrounding sounds or tones throughout the gamut of audible frequencies when actuated by impressed vibratory energy of audible frequency, said diaphragm uniformly increasing in thickness from the center toward the periphery,-

and means for impressing vibratory energy on said diaphragm.

12. A loud speaker comprising a diaphragm having suficient area to produce directly in the surrounding air clearly audible sounds or tones throughout the gamut of andible frequencies when actuated by impressed vibratory energy of audible frequency, said diaphragm having a plurality of zones which progressively increase in thickness from the center toward the periphery and means for impressing vibratory energy on said diaphragm.

In testimony, that l claim the foregoing as my invention, it have signed my name this 17th day of September, 1925.

PERCY W. GR.

air clearly audible.

so I 

